Existing patents:
U.S. Pat. No. 3,996,816, dated Dec. 14, 1976, titled “Harmonic Drive”.
U.S. Pat. No. 3,546,972, dated Dec. 15, 1970, titled “Profile shifted involute internal gearing”.
U.S. Pat. No. 5,324,240, dated Jun. 28, 1994, titled “Eccentric Gear System”.
All the above-mentioned inventions deals with single speed ratio gear drives. In all these inventions it is difficult to have multiple speed ratio gearbox, from which a specific gear ratio can be selected. By using existing eccentric gear drives with turbines as a prime mover, it may be necessary to use a conventional gearbox in series with the eccentric drive.
This invention is based on the work done and applied for international patent bearing the international patent application number PCT/IN01/00150 dated Aug. 29, 2001; configuration 2 and configuration 4 are specifically used for present work. Using the configurations 2 and 4 it is possible to make an eccentric gearbox to have multiple (two or more) high speed ratios, any of the available speed ratios can be selected between input and output shaft by employing a suitable gear engagement mechanism. Though eccentric gearbox with any number of speed ratios can be made with following methodology, only three speed ratio gearboxes are explained below.
Definitions:
Internal gear—A circular gear with internal teeth.
External gear—A circular gear with external teeth.
Fixed gear—The gear with fixed orientation.
Moving gear—The gear that rotates about its own axis.
Pitch circle—A reference circle on the plane normal to the rotational axis of the gear, the diameter of the pitch circle is used for calculations.
Pitch Cylinder—A cylinder, co-axial to the rotational axis of the gear, that passes through the pitch circle of the gear. As most of the time the gear cross section is referred, only pitch circle is referred in the explanation that follows.
Point of contact—Theoretical common point on the pitch circles of the two meshing gears. The two pitch circles are tangential to each other on this point.
Line of contact—Theoretical common line on the pitch cylinders of the two meshing gears. The two pitch cylinders are tangential to each other on this line. This line is always parallel to the axes of the two gears and passes through the point of contact. As most of the time the gear cross section is referred, only point of contact is referred in the explanation that follows.
Eccentricity—Half the difference between the pitch circle diameters of the two meshing gears forming eccentric gear pair as in FIG. 1, FIG. 2 and FIG. 3. The eccentricity should preferably be same for all eccentric parts related to a particular gear pair.
Introduction:
A gearbox with large speed ratio is very useful. This type of gearbox uses eccentric gear pair for obtaining large speed ratio; this makes it-very compact in size for large speed ratio. With an eccentric gearbox, it may be possible to use a turbine as a prime mover for automobiles and for many other applications, without use of conventional gearbox. Use of such a gearbox can make very compact turbine-gearbox unit and can replace the conventional reciprocating engine-gearbox unit in future. An eccentric gearbox can allow utilizing the benefits of using turbine over the use of reciprocating internal combustion engine.